First off 2000 XJ with 122K miles. My a/c supposedly quit on me 4 years ago. took it in two weeks ago to get fixed. Somehow it just needed evac'd and oiled and recharged. Been blowing great for two weeks and no apparent leaks anywere. On to the problems

The day I picked it up and still everytime I start it, it kicks right on but the idle drops and then within a second immediately revs up to normal operating rpms. Its really weird its like starter kicks it on, but it takes it a second to fully get fuel or spark? not real sure. Gas is always ethanol free, has new 784 injectors, good air filter, newer plugs, I take really good care of my Jeep. It really happened right after a/c started to work. so what could I even do to diagnose this?

second problem, today I pulled in to get gas, got gas and went to fire it up and it just cranked and cranked. let it sit like 10 seconds and fired right up. Never ever done this to me before. ( I know my year has really bad heat soak but in the last 4 years its never done this and it was only 89 today.... usually it runs rough for 10 seconds then smooths out) So I drive about 10 more miles stop somewhere and back in within 5 minutes and it does it again. just cranks and cranks, leave it for a bit and fires right up

Just don't see how fixing my a/c has given me two new problems all the sudden

 

Your fuel pump may be on its way out. Put a pressure gauge on it and check running psi, see if it fluctuates. I think norm running is 39.

 

Ok i will look into that, but why would it show no signs of problems one day and be going bad the next? Is it just a coincedence maybe?

 

"but why would it show no signs of problems one day and be going bad the next?"

 

If you are going to check your fuel pressure at the fuel rail, the normal pressure for your year XJ is 49.2 psi +/- 5 psi. The fuel pressure gauge needle may fluxuate rapidly due to the useless damper on the fuel rail.

Check the fuel pressure at idle and at 2000 RPM.

 

Thanks CCKen, I will clean those and check my pressure tomorrow hopefully.

 

So cleaned the TB, IAC, air filter is new. Checked my fuel pressure. Had 40 when i turned it to "run or on" before i cranked it up for first time in 6 days. Ran for 10 mins at 45psi and held at 38-42psi for 2 hours after i shut it off.

Still starts fine on first turn of key, but still does the weird deal where it takes a second and fires up to normal rpm's.

Sometimes i even have to give it a tiny bit of gas to make it shoot up to correct rpms. Could it be my fuel pump going out? Or is it electrical related?

 

And sometimes it wont fire up when ive driven it in last 30 mins or so. Just cranks and cranks. Eventually i wait and it will do its weird start and run fine.

Idles fine, drives 70 down the highway. Just having weird initial start up problem

 

Nevermind... Found the problem, Finally


15 amp mini fuse in engine fuse box was in a blank, not its slot. Must have misplaced it during a/c revival!

 

oof, I hope you had yourself a good face palm for that.

 

Well i didnt do it. Guys that recharged the system must have. Had the compressor unplugged and forgot to tell them. Guess they were searching around the fuse block and misplaced one. Oh well!